Changes In Rate Of Reduction Research Articles

Length Determination of the Solar Greenhouse North Wall in Lanzhou

Abstract In order to determine the optimal length of the greenhouse north wall in Lanzhou, this paper uses the Ecotect and Energyplus v8.6 to evaluate the effect of length of the greenhouse north wall on its indoor thermal environment. Then, the total heat storage/release capacity and the reduction rate of the shadow were proposed. The results show that under different weather conditions, the maximum shadow rate of the east and the west walls of the winter solstice appear at 10:00 in Lanzhou. With the length of the north wall increases, the reduction rate of the shadow gradually decreases, and when the length increases to about 90m, the shadow reduction rate changes smaller. The total heat storage capacity basically equals to its total heat release in a sunny day. While the length is more than 90m, the total heat release is greater than the total heat storage, and the indoor air temperature is lower than that of 90m in next day morning in typical cloudy day. Combined with the needs of the ventilation and insulation in solar greenhouse, the optimal length of north wall of solar greenhouse is about 90m in Lanzhou. The results can provide a reference for the scientific construction of the solar greenhouse in Lanzhou.

The role of eddies inside pores in the transition from Darcy to Forchheimer flows

[1] We studied the role of intra-pore eddies, from viscous to inertial flows, in modifying continuum-scale flow inside pores. Flow regimes spanning Reynolds NumberRe∼ 0 to 1350 are divided into three zones – one zone follows Darcy flow, and the other two zones describe non-Darcy or Forchheimer flow. During viscous flows, i.e.,Re 1, and their growth leads to the deviation from Darcy's law and the emergence of Forchheimer flow manifested as a characteristic reduction in the apparent hydraulic conductivity Ka. The reduction in Ka is due to the narrowing of the flow channel which is a consequence of the growth in eddies. The two zones of Forchheimer flow correspond to the changes in rate of reduction in Ka, which in turn are due to the changes in eddy growth rate. Since the characteristics of Forchheimer flow are specific to pore geometry, our results partly explain why a variety of Forchheimer models are expected and needed for different porous media.

Change in metabolic pathways in hybridoma growth and monoclonal antibody production

Abstract The growth and monoclonal antibody production kinetics of a murine hybridoma cell line, A3, were investigated under the exponential growth condition in batch culture. The growth yields for both glucose and glutamine increased in the middle of their exponential growth phase. The lactate yield from glucose was reduced at the late stage of culture, while the specific oxygen uptake rate was unchanged during the exponential growth, suggesting that more glucose flux enters the tricarboxylic acid cycle [TCA cycle] to synthesize ATP during catabolism at the late stage of the exponential growth phase than at the early stage. The monoclonal antibody (MAb) yields for both glucose and glutamine were also enhanced by around twofold, whereas the specific MAb production rate was reduced by 27% at the late stage of the culture. We calculated the specific ATP synthesizing rate, qATP, and found that it is reduced by 24% at the late stage of culture. We also found that the cell size and the protein content in a cell were reduced by 7%, equivalent to 21% of the cell volume change, and by 13%, respectively. These changes in reduction rates and the specific MAb production rates approximately agree with those in the ATP synthesizing rate during the exponential growth.

Chimeric cDNA expression and site directed mutagenesis studies of cytochrome P450s CYP2A1 and CYP2A2

Construction of chimeras and site directed mutagenesis were used to study the regioselectivity and kinetics of testosterone hydroxylation by the cytochrome P450s CYP2A1 and CYP2A2. Although these enzymes exhibit 88% sequence similarity, they catalyze very different regioselective hydroxylations of testosterone. Active chimeras inwhich the first 355 amino acids do not correspond to a single enzyme show broad radioselectivity, whereas the specificity of the parent enzyme is obtained if the first 355 amino acids are unchanged. Therefore, the region between amino acids 275 and 355 is important in maintaining regioselectivity. Single point mutants were constructed for the 13 amino acid differences in this region. For 26 single point and 2 double mutants all active mutants have the same regioselectivity as the parent enzymes. However, kinetic analysis of the CYP2A1 mutants showed that 4 single point mutants and 1 double mutant had kinetic parameters very different from the parent enzyme. All of these substitutions are associated with the conserved dioxygen binding region of the putative I helix predicted from the crystal structure of P450(cam). Deuterium isotope effects were used to determine any changes in the rate of reduction and to estimate the relative amount of excess water formation. Changes in reduction rates are not sufficient to account for the differences in V(max) values. Therefore, it is likely that the amount of hydrogen peroxide formed is a primary determinant of V(max).

Determination of the equilibrium constant for the binding of ferricytochrome c to phospholipid vesicles and the effect of binding on the reduction rate of cytochrome c

The rate of reduction of cytochrome c by 2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine was examined as a function of binding to liposomes prepared from mixed soybean phospholipids, asolectin, and from various purified phospholipids. Binding of cytochrome c to asolectin liposomes caused an increase in the rate of reduction by the pteridine derivative from 2900 to 16 000 M-1 x s-1 at pH 7. At low ionic strength (0.003 M) the binding stoichiometry between cytochrome c and asolectin vesicles is 15 +/- 2 phosphospolipid/cytochrome c (mole ratio), determined by monitoring the change in reduction rate of cytochrome c by pteridine as cytochrome c is bound to the vesicles. A stoichiometry of 14 phospholipid/cytochrome c was obtained from gel filtration studies. Equilibrium association constants for the binding of cytochrome c to sites on the asolectin vesicles varies from 2.2 x 10(6) to 1.8 x 10(3) M-1 between 0.02 and 0.10 M ionic strength, respectively. In general, liposomes prepared from purified phospholipids resulted in less binding of cytochrome c per mole of phospholipid and lower reduction rates than those prepared from asolectin.